1. The Field of the Invention
The present inventions related to syringes, and more particularly to variable low flow syringes for delivering fluids to a work area.
2. The Relevant Technology
Many dental, medical, and other procedures require the delivery of fluids to a specific work area in very precise quantities. Accordingly, a fluid delivery system must be able to deliver the fluid to a specific work location in precise amounts that can be closely controlled by the user. In some applications, the work area is easily and directly accessible to the user.
Various types of squeezable fluid delivery systems have been developed to deliver fluids to a precise work area. Fluid is dispensed by squeezing the container or the dispensing tip. While the squeezable fluid delivery system aids in the accurate placement of fluid, there is nothing to prevent the accidental discharge of the fluid adhesive if the user slips or the container of fluid is squeezed too hard. Accidental or excess discharge of fluid from the container is particularly problematic with low viscosity fluids such as acetone, water, or alcohol. In addition, this fluid delivery system may only be used if there is direct unimpeded access to the worksite.
The most commonly used fluid delivery system is a syringe. Fluids are delivered to a specific work area using a syringe in a variety of situations. Typical syringes include a barrel and a plunger. The barrel acts as a fluid reservoir and the plunger is disposed in the barrel. Fluid is pushed out of the fluid reservoir when the plunger is depressed. The syringe has some type of tip attached to the end of the barrel for delivering fluid to a specific work area.
During use, a syringe is typically held in one hand. The other hand is usually busy keeping the work area clean or holding something. The user of the syringe must usually hold the syringe in one hand and depress the plunger with the same hand that is holding the syringe. It is important that the plunger be depressed with a great deal of control to insure that the correct amount of fluid is forced out of the syringe. It is difficult to precisely control how far the plunger is depressed and correspondingly how much fluid is dispense. The control problem becomes even more accentuated when this type of fluid delivery system is used with fluids having a low viscosity and, consequently, requiring little force to discharge the fluid from the barrel. An accidental slip while depressing the plunger can easily empty the entire fluid reservoir of a low viscosity fluid.
Syringes are often used as a fluid delivery system in dental procedures. In dental procedures, the worksite tends to be remote and difficult to reach because of space limitations. As previously mentioned, it is often difficult to control the delivery of the fluid to the specific work area. In many dental procedures, it is important to deliver small, discrete quantities of fluid.
Another problem associated with conventional syringes, particularly prefilled syringes, is evaporation or leakage of a fluid from the barrel or fluid reservoir of the syringe. Syringes, such as those used in dental procedures, are often prefilled with the desired fluid prior to being stored and shipped to a customer. Such prefilled syringes are often utilized to deliver a certain volume of fluid so it is preferable for the volume to remain constant during shipping and storage. Evaporation is a particularly challenging problem as many of the fluids that are used with the dental syringes are volatile or are fluids that have a low viscosity. Accordingly, when a dentist is ready to use a syringe containing a fluid with a high content of a volatile fluid such as alcohol there may be significantly less fluid in the syringe compared to when it was filled. Not only is this frustrating to the customer, but the leakage and evaporation of volatile fluids may compromise certain procedures due to delivery of an inadequate amount of fluid.
One method of minimizing the problems associated with potential leakage or evaporation is to attach a tip or cap to the syringe prior to shipping or storing the product. Using tips to minimize the problems of leakage and evaporation is problematic as the tip attached to a syringe during shipping may not be the tip desired by the end user, such as a dentist, for a particular procedure as there are a variety of tips which are each optimal for different procedures. The result is a decrease in efficiency for the user of the syringe as it is then necessary to take the time to change the tips. To avoid the need to change tips, manufacturers can make syringes available containing identical fluids with different tips. This increases the inventory costs of the manufacturer which increases the price of the syringe.
Caps are generally more effective than tips in reducing evaporation, however, there are also problems associated with the use of caps. Caps decrease the efficiency of procedures involving such syringes and increase the costs of such syringes as the cap must be replaced by a tip for use in delivering the fluid.
In addition, neither tips or caps completely solve the problems of evaporation or leakage of fluids from syringes. Accordingly, it would be advantageous to have a fluid delivery system, such as a syringe, that can be prefilled with a desired fluid and then stored and shipped with substantially no leakage or evaporation of the fluid. It would also be advantageous to be able to store and ship prefilled syringes without a tip or a cap.
In conclusion, it would be advantageous to have a fluid delivery system that will deliver only drops of fluid. There are certain situations where initially only drops of fluid are needed and later a steady or increased flow of fluid is required. It would be advantageous to have a fluid delivery system that is configured to provide sufficient control to deliver fluid a drop at a time as well as being able to gradually increase the flow rate to a stream of fluid.